The invention relates to an encoding method for creating a video data stream for an extension signal. Furthermore the invention relates to a decoding method for reconstructing an extension signal from a video data stream and a base signal. Furthermore the invention relates to an encoding device for creating a video data stream and a decoding device for reconstructing an extension signal.
For many applications digital visual signals are to be provided at a plurality of image quality levels. On the one hand these digital, visual signals are to be decoded and displayed on different reproduction devices, such as on a television set and also on a mobile terminal (e.g. mobile telephone) for example. On the other hand the digital visual signals are to be transferred over a plurality of transmission channels to the widest variety of devices. Thus a transmission bandwidth of several megabits per second is available in a cable network, whereas a transmission bandwidth in a mobile radio channel on the other hand possibly amounts to only a few thousand bits per second.
Concepts K. Illgner et al., “Efficient encoding of video signals for scalable multicast storage and transmission as well as associated codec,” Publication No. DE 102 00 901 A1; and P. Amon et al., “Prediction of video signal levels for scalable simulcast storage and transmission,” file reference of German Patent Application No. DE 101 46 220.4 are already known in which a digital visual signal is made available at a plurality of quality levels. The digital visual signal that represents the lowest quality level is referred to as the base signal. In documents K. Illgner et al., “Efficient encoding of video signals for scalable multicast storage and transmission as well as associated codec,” Publication No. DE 102 00 901 A1; and P. Amon et al., “Prediction of video signal levels for scalable simulcast storage and transmission,” file reference of German Patent Application No. DE 101 46 220.4 the individual digital visual signals are not encoded independently of each other for this purpose, but a digital visual signal of a higher quality level is derived from one or more digital visual signals of lower quality levels (differential encoding). A differential digital visual signal of a higher quality level is referred to as an extension signal. To guarantee efficient differential encoding, the individual encoders of the various quality levels are synchronized P. Amon et al., “Method for encoding and decoding of video sequences and computer program product,”Publication No. DE 102 19 640 A1. Synchronization in this context means that decisions relating to the encoding of an image are only taken once, e.g. determining a motion vector, and then the encoders of the different quality levels are notified.